Presently, underground shock-resistant structures generally have a box-type configuration with flat wall and ceiling slabs. The flat ceiling slabs are necessarily thick and heavily reinforced, particularly as the distance between the walls at opposite sides of the structure increases.
Gallery-type concrete underground structures utilize a small free span but are usually long and straight. Some have been built with barrel vaults. This version, having a vaulted ceiling rather than a flat ceiling, permits minimization of the thickness of the ceiling for a given overpressure coming from above as from a nuclear bomb. However, elongated galleries offer an extended frontage to shockwaves which strike the walls laterally.
Dome-like shelters are unusually heavy structures and become extremely difficult to build as the area encompassed by such shelters increases.
The following prior art, though not exhaustive of underground shock-resistant structures, disclose underground structures of various configurations and shapes for withstanding overpressure.
United States PA0 West German PA0 France PA0 Belgium PA0 Great Britain PA0 European
2,436,196--Starret PA1 709650--Vietoris PA1 1,052,102--Laible PA1 1,143,627--Dyckerhoff et al PA1 2,629,324--Fruhling PA1 808,468--Marchand PA1 1,107,454--Tannerbquer et al PA1 629,907--Franck PA1 507,415--Mueller-Ehlers PA1 1,367--Hirsch et al